High-performance lithium–ion batteries (LIBs) are the main development direction of future energy storage devices. However, most LIBs still face a problem of high first irreversible capacity loss. Pre-lithiation technology can increase the content of active lithium source and compensate the loss of active lithium during the first cycle. Adding lithium supplement additive to the cathode provides an effective way to improve the electrochemical performance of LIBs. Here, Li2MoO3 has been investigated as a cathode additive in the full cells. In order to optimize its preparation, Li2MoO3 has been prepared by three different methods, including solid-phase method, liquid-phase method and ultrasonic method. Based on material characterization and electrochemical performance tests, Li2MoO3 material prepared by liquid-phase method shows the best lithium storage properties and chosen as a cathode additive in the LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2/SiO@C full cells. The addition of Li2MoO3 has successfully improved the electrochemical performance of the full cell. The first discharge specific capacity increases from 103.9 mAh g[Formula: see text] to 130.4 mAh g[Formula: see text]. In short, Li2MoO3 material is a promising cathode additive for LIBs.